The present invention relates to a system using a plasma generator in the ECR (Electron Cyclotron Resonance) type, and more particularly, to an ECR plasma generator as an apparatus for deposition and etching on an object to be processed, for example, a semiconductor wafer and an ECR system using the ECR plasma generator.
For example, as a conventional system for etching in a desired shape desired portions of a thin film formed on a semiconductor wafer, dry etching apparatuses are known. An etching comprising parallel plate type electrodes is more popular among them, and the RIE (reactive ion etching) type apparatus and the PE (plasma etching) type apparatus are well known.
In either type, etching gas (reactive gas) is introduced into an etching chamber reduced in pressure to generate plasma so that a thin film on the semiconductor wafer can be etched. The gas pressure is set to be comparatively high, i.e. some hundreds mTorr or higher.
In the etching process under such a comparatively high pressure atmosphere, reactive by-products fly in the chamber as dust (particles). If they fall down on the semiconductor wafer, they will cause drawbacks in the circuit pattern during the production, which degrades the yield of the products.
In the RIE type apparatus, since the physical etching is mainly carried out, ions of high energy, for example, 500-600 eV, are irradiated onto the semiconductor wafer, and the semiconductor wafer may be thereby damaged.
On the other hand, recently, a magnetron plasma system which generates high-density plasma in a comparatively low pressure atmosphere and uses it for deposition and fine etching has been used in practice.
According to this system, the magnetic field is applied horizontally to the semiconductor wafer and the radio frequency field rectangular with the semiconductor wafer is also applied, so as to generate the magnetron discharging for the etching.
In this system, however, since the magnetic field is applied horizontally to the semiconductor wafer, charged particles drift essentially in the direction of the magnetic field, i.e. E.times.B drift occurs.
As a result, there is an essential problem that the plasma density can be unbalanced and irregular at the downstream side and upstream side of the transported charged particles, which causes the charge-up damage of the semiconductor wafer.
On the other hand, a system using the ECR plasma generator as a plasma generator improving the plasma density by using the magnetic field forming technique that can hardly generate essentially the irregularity of plasma caused by the E.times.B drift, has been proposed.
When this system is used, however, since the used frequency is the microwave of some GHz, the resonant magnetic field becomes extremely large. For example, the resonant magnetic field corresponding to the microwave of 2.45 GHz is 875G (G: gauss), which requires a large-size magnet, and the system is not realistic.
Further, large power needs to be supplied to the process chamber. In this case, a waveguide has to be used, which makes the structure of the apparatus complicated.
In order to solve these problems, it is conceived to lower the frequency of the applied radio frequency wave. In this case, however, the Lamor radius of electrons becomes large, the electrons collide with the process chamber walls before the cyclotron movement and thereby lose their energy, which makes it difficult to improve the plasma density.